Over at least the past thirty-five years there has been a continuing interest in the ability to detect and identify particular types of items, such as high-value documents, from afar. A number of methods of item detection have been explored, including visible light examination, magnetic sensing, multispectral analysis, and detection of responses from radio frequency identification (RFID) tags. All of the previous methods have been limited in a combination of precision, range, and general applicability. Known methods for observing target item characteristics require some knowledge of target item behaviors, which may be deliberately designed, and/or close physical access to the target item. Current and past techniques thus require substantial a priori knowledge.